Fix exec -w for relative paths with --root argument

bin/coq/coqtop.ml

@@ -153,7 +153,7 @@ let term =
     in
     Fiber.return (coqtop, argv, env)
   in
-  restore_cwd_and_execve common coqtop argv env
+  restore_cwd_and_execve (Common.root common) coqtop argv env
 ;;
 
 let command = Cmd.v info term

bin/exec.ml

@@ -77,22 +77,25 @@ module Command_to_exec = struct
 
   (* Helper function to spawn a new process running a command in an
      environment, returning the new process' pid *)
-  let spawn_process path ~args ~env =
+  let spawn_process ~root path ~args ~env =
     let pid =
-      let path = Path.to_string path in
+      let prog = string_path_relative_to_specified_root root (Path.to_string path) in
       let env = Env.to_unix env |> Spawn.Env.of_list in
-      let argv = path :: args in
+      let argv = prog :: args in
       let cwd = Spawn.Working_dir.Path Fpath.initial_cwd in
-      Spawn.spawn ~prog:path ~env ~cwd ~argv ()
+      Spawn.spawn ~prog ~env ~cwd ~argv ()
     in
     Pid.of_int pid
   ;;
 
   (* Run the command, first (re)building the program which the command is
      invoking *)
-  let build_and_run_in_child_process { get_path_and_build_if_necessary; prog; args; env } =
+  let build_and_run_in_child_process
+    ~root
+    { get_path_and_build_if_necessary; prog; args; env }
+    =
     get_path_and_build_if_necessary prog
-    |> Fiber.map ~f:(Result.map ~f:(spawn_process ~args ~env))
+    |> Fiber.map ~f:(Result.map ~f:(spawn_process ~root ~args ~env))
   ;;
 end
 
@@ -139,18 +142,18 @@ module Watch = struct
 
   (* Kills the currently running process, then runs the given command after
      (re)building the program which it will invoke *)
-  let run state ~command_to_exec =
+  let run ~root state ~command_to_exec =
     let open Fiber.O in
     let* () = Fiber.return () in
     let* () = kill_currently_running_process state in
     let* command_to_exec = command_to_exec () in
-    Command_to_exec.build_and_run_in_child_process command_to_exec
+    Command_to_exec.build_and_run_in_child_process ~root command_to_exec
     >>| Result.map ~f:(fun pid -> state.currently_running_pid := Some pid)
   ;;
 
-  let loop ~command_to_exec =
+  let loop ~root ~command_to_exec =
     let state = init_state () in
-    Scheduler.Run.poll (run state ~command_to_exec)
+    Scheduler.Run.poll (run ~root state ~command_to_exec)
   ;;
 end
 
@@ -294,7 +297,7 @@ module Exec_context = struct
     in
     let prog = Path.to_string path in
     let argv = prog :: args in
-    restore_cwd_and_execve common prog argv env
+    restore_cwd_and_execve (Common.root common) prog argv env
   ;;
 
   let run_eager_watch t common config =
@@ -322,7 +325,7 @@ module Exec_context = struct
       ; env
       }
     in
-    Watch.loop ~command_to_exec
+    Watch.loop ~root:(Common.root common) ~command_to_exec
   ;;
 end
 

bin/import.ml

@@ -237,14 +237,12 @@ module Scheduler = struct
   ;;
 end
 
-let restore_cwd_and_execve (common : Common.t) prog argv env =
-  let prog =
-    if Filename.is_relative prog
-    then (
-      let root = Common.root common in
-      Filename.concat root.dir prog)
-    else prog
-  in
+let string_path_relative_to_specified_root (root : Workspace_root.t) path =
+  if Filename.is_relative path then Filename.concat root.dir path else path
+;;
+
+let restore_cwd_and_execve root prog argv env =
+  let prog = string_path_relative_to_specified_root root prog in
   Proc.restore_cwd_and_execve prog argv ~env
 ;;
 

bin/ocaml/utop.ml

@@ -56,7 +56,7 @@ let term =
          ~f:(fun dir env -> Env_path.cons ~var:Ocaml.Env.caml_ld_library_path env ~dir)
          ~init:env
   in
-  restore_cwd_and_execve common utop_path (utop_path :: args) env
+  restore_cwd_and_execve (Common.root common) utop_path (utop_path :: args) env
 ;;
 
 let command = Cmd.v info term

bin/tools/ocamllsp.ml

@@ -51,7 +51,7 @@ let term =
       let open Fiber.O in
       let* () = Lock_dev_tool.lock_ocamllsp () |> Memo.run in
       let+ () = build_ocamllsp common in
-      run_ocamllsp common ~args)
+      run_ocamllsp (Common.root common) ~args)
 ;;
 
 let info =

doc/changes/10982.md

@@ -0,0 +1,2 @@
+- Fix exec -w for relative paths with --root argument (#10982,
+  @gridbugs)

test/blackbox-tests/test-cases/exec-watch/exec-watch-multi-levels.t/run.t

@@ -22,8 +22,10 @@ Perform the same test above but first enter the "bin" directory.
   Success, waiting for filesystem changes...
   foo
   Leaving directory '..'
+  $ PID=$!
   $ cd ..
-  $ wait
+  $ ../wait-for-file.sh $DONE_FLAG
+  $ kill $PID
 
 Test that the behaviour is the same when not running with "--watch"
   $ cd bin && dune exec --root .. ./bin/main.exe